The invention relates to a method for regulating an electric-motor-driven adjusting device, for instance for power windows, a sunroof or the like, and in particular for vehicles with a safety circuit for reversing a drive motor, for example, for the power windows or sunroof, and to an apparatus for performing the method.
An electric-motor-driven adjusting device for automobiles of the type defined at the outset is known, for instance from German Patent DE 33 03 590 C2. In it, a safety circuit is provided which reverses the direction of motion of the window if in its upward motion the window meets some resistance, such as a hand or head of a person.
Often, the occurrence of pinching, i.e. of something being caught when closing an opening, is detected by detecting the motor rpm, which drops if a load occurs. The time required to detect a change in rpm, however, is comparatively long, so that in the event of pinching, injuries or at least pain can occur until the window is finally reversed. To shorten the detection time, it is conceivable to use more-powerful processors in the open-loop control system, but these are expensive.
With this as the point of departure, it is the object of the invention to disclose both a method for regulating an electric-motor-driven adjusting device, especially for vehicles, with a safety circuit for reversing a drive motor of the adjusting device, and an apparatus for performing the method, by which safe and fast detection of pinching is made possible. Furthermore, effects caused for instance by poor pavement or the effects of weather (especially in winter) should not be detected as a pinching situation.
In terms of the method, this object is attained essentially in that an actual value is regulated via a control circuit, in particular a closed-loop control circuit, to a set-point value, the actual value and the set-point value are signals proportional to the rpm or load on the drive motor, and a deviation of the actual value from the set point value is detected with a comparison member of the control circuit and is utilized both to adjust the actual value (motor rpm or load) and to activate the safety circuit.
In this method, the properties of a closed-loop control element are advantageously exploited. The response of an actual closed-loop control element is at its fastest simultaneous with the change at the input. The rate of change and the characteristic at the output are also definable. As part of a control circuit, the controller seeks to regulate a generated control difference or deviation to 0. This deviation serves as a basis for an algorithm for assessing any pinching situations that might occur. Other similar but harmless factors, such as accelerations caused by driving on stretches of bad road, sluggishness of the power window or sunroof system, and properties that are changed by the effect of climate are compensated for by the controller, since they differ from the harmful pinching situations in the characteristic and speed of occurrence. This provision serves to enhance closing safety, for instance when driving on bad roads as noted above. The method is used above all to detect dangerous situations when closing a window or sunroof using an electric-motor-driven drive, to prevent injuries from the pinching forces then operative. Despite the sensitivity of the method to dangerous pinching situations, and the short time available for possible detection, a high degree of closing safety is attained. Acceleration factors from outside, of the kind caused by driving on so-called stretches of bad road do not lead to the detection of a pinching situation and thus to the associated erroneous reversal. Nor is the influence of existing and weather-dictated sluggishness of the system assessed as a pinching situation, and thus the window or sunroof or the like can be closed unimpeded. The method is suited to distinguishing these factors from the dangerous pinching situations.
In an advantageous refinement of the invention, an actual frequency is compared with a set-point frequency, and from the phase deviation between the set-point frequency and the actual frequency, a controlling variable or deviation is derived, by which a safety circuit is activatable.
This embodiment makes use of the fact that every change in frequency results in a change of phase, but the change of phase makes substantially faster detection possible than a change of frequency. It can be appreciated that only the edges corresponding to one another of the frequency signals of the set-point frequency and actual frequency have to be compared with one another in order to obtain a deviation, from which a controlling variable can then be derived.
In a further advantageous concept of the invention, the phase deviation or differential signals are integrated over a predetermined period of time and from the integral the controlling variable or deviation is derived, by which the safety circuit is activatable if a certain threshold value is exceeded. For instance if an obstacle appears in the path of displacement of the window, this makes itself felt in a drop in the motor rpm. The result is a phase deviation between the actual frequency and the set-point frequency. From these differential signals, a controlling variable or deviation is determined. If within a predetermined length of time a plurality of such differential signals then occur, the controlling variable or [standard] deviation passes a certain threshold value, and the system detects an obstacle and reverses the drive motor of the power window. The safety circuit can also be activated by means of a microprocessor and a suitably adapted algorithm.
If periodic loads are exerted on the window because of bumpy roads, change in motor rpm, which in turn can be detected in a phase difference between the set-point frequency and the actual frequency. These phase changes are alternating pulses. However, the integration of these differential signals over a predetermined length of time is essentially 0, so that the threshold value is not passed. As a result, effects caused by bumpy roads are precisely not detected as a pinching situation, and activation of the safety circuit does not ensue.
In a further concept of the invention, a set-point frequency is predetermined by an external set-point frequency transducer and compared with an actual frequency determined by the rpm of the drive motor. The mode of operation of the control circuit is based on a readjustment of the motor rpm, which determines the actual frequency, to the predetermined value of the external set-point frequency.
Alternatively, a set-point frequency determined by the rpm of the drive motor is predetermined. A voltage-controlled oscillator readjusted by the controlling variable or deviation forms a fixed-phase actual frequency. The actual frequency is then returned to the phase detector and compared again with the set-point frequency. If the set-point frequency has changed because of an obstacle in the displacement path, then a phase deviation is detected. In the next cycle, the readjusted voltage-controlled oscillator generates an actual frequency that is fixed in phase with regard to this predetermined set-point frequency.
In terms of the apparatus, the object is essentially attained by a control circuit having a set-point value transducer and an actual value transducer, in which as the set-point value or actual value, a signal proportional to the rpm or load of the drive motor is processed, and having a comparison member for forming a deviation, the deviation being delivered to a detection stage which activates the safety circuit.
An advantageous refinement is formed by a control circuit with a set-point frequency transducer, an actual frequency transducer, and a phase detector, which as a comparator forms a phase difference between the set-point frequency and actual frequency, and with a controller which from the phase difference determines a controlling variable for the control circuit, by which controlling variable the actual frequency is readjusted. The safety circuit is activatable by evaluation of the deviation.
In a refinement of the invention, the drive motor of the power window is coupled to an rpm transducer, which is embodied as an actual frequency transducer and as its actual frequency generates a frequency signal that is proportional to the rpm of the drive motor, so that a change in the rpm of the drive motor is immediately detected by the control circuit as a change in actual frequency.
The phase detector is embodied as a digital PLL phase detector, for instance. At its output, this PLL phase detector furnishes the result of the comparison of the set-point frequency and the actual frequency, in the form of a digital voltage, which acts as a deviation. The phase relationship of the actual frequency and set-point frequency to one another is accordingly reflected in the pulse length of the voltage signal output at the output of the PLL phase detector.
The PLL phase detector is advantageously edge-triggered. As a result, it is not necessary for all the frequency signals to be compared, but only one edge, which is entirely adequate for ascertaining the phase relationship of the two frequencies.
In an advantageous feature of the invention, the set-point frequency transducer is embodied as an external frequency generator, which generates the set-point frequency as a reference variable. As a result, a constant reference frequency is available at the phase detector, and with the aid of this frequency, any deviation in the actual frequency of the drive motor can be detected by the phase detector.
A particular feature of the invention provides that the controller is embodied as an analog integral controller. It is thus possible for the voltage pulses that appear at the output of the PLL phase detector as a consequence of the phase displacement of the set-point frequency and actual frequency to be integrated. Preferably, an integration of the differential signals appearing at the phase detector takes place over a certain time interval. In the event that, upon the integration of the voltage signals, a predetermined, optionally variable-time or variable-parameter direct voltage level is passed, the system reacts to an obstacle in the displacement path of the window and reverses the drive motor. The phase differences between the set-point frequency and actual frequency, which occur as a consequence of bumpy roads, have alternating voltage signals, so that the integration over a certain time interval is essentially 0, and thus the direct voltage level is not undershot. Hence bumpy roads are not detected by the control circuit as a pinching situation.
In another advantageous feature of the invention, the control circuit includes an rpm controller for the drive motor, which as a function of the pulses at the output of the PLL phase detector generates an analog controlling variable. The controlling variable is then supplied to a pulse width modulator with a switching transistor, which converts them into a digital voltage by which the actual frequency of the drive motor is readjusted to the set-point frequency of the external set-point frequency transducer if, for example because of weather factors, the friction resistance of the window increases and thus the rpm of the drive motor drops.
In terms of the apparatus, a second way of attaining the object, which is based on the same principle, is that the rpm transducer, coupled to the drive motor of the power window, is embodied as a set-point frequency transducer and as its set-point frequency generates a frequency signal which is proportional to the rpm of the drive motor.
An especially advantageous feature of the invention is that as the actual frequency transducer, a readjusted voltage-controlled oscillator (VCO) is embodied, which generates the actual frequency as a comparison variable to the set-point frequency. By using this kind of readjusted voltage-controlled oscillator, in combination with the drive motor embodied as a set-point frequency transducer, the use of electronics for readjusting the drive motor rpm becomes unnecessary.
In a further feature of the invention, the controller is embodied as an analog proportional-integral controller. The voltage pulses that arrive from the PLL phase detector are now assessed twice by this proportional-integral controller. First, via the integral member of the proportional-integral controller on passing a certain voltage level, the safety circuit is again activated. The proportional-integral controller, analogously to the integral controller of the first version, detects that in the event of bumpy roads, a pinching situation is not involved. Second, via the proportional member of the proportional-integral controller, the operating point of the voltage-controlled oscillator is tracked. From this signal, this oscillator then generates an actual frequency, which is in fixed phase with the original set-point frequency. The actual frequency is then returned to the PLL phase detector, where it is again compared with the set-point frequency. From the phase difference, the PLL phase detector generates a digital voltage signal, which is delivered to the proportional-integral controller.
It is also an essential advantage of the invention that no processor is needed to detect the phase displacement, so that detecting pinching can be done entirely with the existing processor in the vehicle. It is understood, however, that pinching can also be detected by means of a microprocessor.
It is understood that the detection stage for activating the safety circuit can be embodied either in analog fashion or by means of a microcontroller or microcomputer. In the case where a microcomputer is provided, a special algorithm is furnished for detecting the pinching situation. Particularly for detecting a stretch of bad road, the deviation or controlling variable is analyzed accordingly, to avoid so-called erroneous reversals. Erroneous reversals of the drive are understood to mean situations in which a pinching situation is not occurring, but the course of the rpm change of the motor of the adjusting device, for other reasons, at least briefly has a course similar to that in the pinching situation. By analysis of the deviation or controlling variable, either in analog fashion or by means of a microcomputer and a corresponding algorithm, such erroneous reversals of the drive are suppressed. Fluctuations in the on-board electrical system, for instance of the motor vehicle, can under some circumstances also affect the regulation or reversal of the drive motor. This is true particularly for brief major fluctuations in the on-board voltage, since electrical system fluctuations that vary more slowly are readjusted within the control speed of the control circuit and generally do not cause erroneous reversals. Major fluctuations in the system voltage that occur suddenly cannot be detected as such by the actual control circuit, since they can also cause a major change in the motor rpm. Nevertheless, the safety circuit should not reverse if such a case is detected. This can be accomplished for instance by providing that if a major voltage fluctuation in the on-board electrical system is detected, the regulation is briefly deactivated, or the threshold value is adapted to the changed signals. Such suddenly occurring major fluctuations are detected for example via a voltage divider or a capacitor circuit.